Standard tracking technologies are often based on either radio frequency (RF) or acoustic propagation and use time-flight or relative phase information to determine distance from a known transmit location. Whilst such technologies function without difficulty in open areas, applying these technologies to indoor multi-path environments with the reflections from floors, walls and other obstacles has encountered serious difficulties.
U.S. Pat. No. 4,282,485 presents a typical prior art inductive position sensor. In this particular patent application, the inductive position sensor is a so-called linear variable phase transformer (LVPT) incorporating two primary coils and a secondary coil, each formed by a plurality of generally circumferential turns of respective conductors about a non-magnetic bobbin. Within a hollow interior of the bobbin, a core is positioned for movement relative to the two primary coils and a secondary coil along the axis. This position sensor is therefore only capable of determining the core's position along a single axis. Since the coils need to be arranged about a bobbin it would be particularly impractical and almost impossible to scale up such systems to fit around living spaces to determine the position of tags placed therein.
One of the objectives of the present invention is to provide a position sensor which contrary to the sensor described in the context of the above prior art document is particularly well suited for operation within conventional living spaces such as offices, warehouses, factory floors etc. As part of this objective, the invention presents a position sensor which does not unduly protrude from ceilings or walls so as to facilitate straightforwvard retro-fitting without unduly burdening the aesthetics of any particular living space.
It is a further objective of the present invention to present a position sensor capable of determining the position of a tag in any position in the X, Y and Z planes.
It is also an aim of the present invention to provide tag means whose position may be determined irrespective of its own orientation, so that for example the tag's position may be determined while it is being rotated by an operator.
It is a further objective of the present invention to present a variety of processing means for use in sensors with particular operating properties, in order to maximise the operational efficiency of individual applications.
The present invention aims to provide a particularly versatile system which may be scaled up or scaled down to meet any particular requirement. The invention will particularly describe how a matrix of position sensors may be employed to monitor the position of tags throughout a collocation of living spaces such as a building.